And that's that

(and) that's that

That is final; the issue is settled or completed. You are going to your sister's recital and that's that! No more complaining. That's that! I just send the proofs to the printer. Let's just say that's that and be done with it.
See also: that

And that's that.

That is final and nothing more needs to be said. I refuse to go with you and that's that!
See also: and, that